Microscope and Microscopy - Where do we use Microscopes?-advanced

Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye. In Grade 9 Biology, this is fundamental for studying the cell, the basic unit of life.

Magnification ($M$) is the process of enlarging the apparent size of an object. Total magnification in a compound microscope is the product of the magnification of the objective lens and the ocular lens: $M_{total} = M_{objective} \times M_{ocular}$.

Resolving Power (Resolution) is the ability of an optical instrument to show two close objects as separate. The limit of resolution ($d$) is determined by the wavelength of light ($\lambda$) and the numerical aperture ($NA$).

The Compound Light Microscope is used in laboratories to observe living cells, stained sections of tissues, and microorganisms. It uses visible light ($400 \text{ nm}$ to $700 \text{ nm}$) and glass lenses.

The Electron Microscope (EM) uses a beam of electrons instead of light. Because the wavelength of electrons is much shorter than that of visible light, EM can achieve magnifications up to $2,000,000 \times$, allowing us to see organelles like ribosomes and DNA.

Applications in Microbiology: Identifying pathogens like bacteria ($1-10 \: \mu m$) and viruses ($20-300 \: nm$). For example, observing the structure of $Escherichia \: coli$ requires high resolution.

Applications in Histopathology: Surgeons and pathologists use microscopy to examine biopsy samples to detect cancerous cells, which often show abnormal nuclear-to-cytoplasmic ratios ($N:C$ ratio).

Forensic Science: Using microscopes to analyze trace evidence such as hair, fibers, or glass fragments found at a crime scene.